The invention relates generally to pneumatic control valves or control valve systems for selectively controlling the movement of pneumatically-operated devices or systems, such as pneumatically-actuated cylinders, clutches, or brakes, for example, used to operate various pneumatically-operated devices, such as presses, linkages, etc. More particularly, the present invention relates to such pneumatic control valve systems that are adapted to conserve energy by minimizing the pneumatic air pressure needed during certain parts of the operation, as well as being adapted to compensate for, and monitor, any air leakage in the pneumatically-operated device or in the overall system.
Pneumatic control valves or control valve systems are commonly used in various operations or processes for controlling the flow of pressurized control air to and from a pneumatically-operated cylinder or other such actuating device having a movable work-performing member or armature. Frequently, however, the pneumatically-operated device is not constantly in motion, with the work-performing member being held in a stationary position during various portions of the operation. The maintaining of full line control air pressure during periods when the movable armature of the pneumatically-operated device is required to be held in a stationary position has been found to be wasteful of energy required to run compressors or other such devices. In addition, in many pneumatically-operated systems, especially in systems employing older equipment, leakage inevitably occurs in the pneumatically-operated device or in related systems or subsystems. The maintaining of full line control air pressure and flow in order to compensate for such leakage has also been found to be expensive and wasteful in terms of energy usage, especially in systems such as those described above wherein a movable armature is required to be held in a stationary position during various portions of the operation of the system.
Accordingly, the need has arisen for a pneumatic control valve or control valve system that is capable of addressing the above-mentioned problems in a more energy-efficient manner. To this end, in accordance with the present invention, it has been found that a pneumatically-operated cylinder or other such device can be held in a stationary or static condition with approximately thirty percent to forty percent of the air pressure needed for dynamic operation. In addition, it has been found that it is not necessary to continuously and instantaneously compensate for leakage in the pneumatically-operated system or device, especially during the above-mentioned static modes of operation.
Accordingly, the present invention provides an improved pneumatic control system selectively deactuable and actuable for controlling movement of the armature of a pneumatically-operated device between first and second working positions, respectively, with the control system having a control air inlet port connected to a source of pressurized control air, at least one exhaust outlet port, at least first and second supply ports for selectively supplying control air to forcibly actuate the pneumatically-actuated armature to the first and second working positions, respectively, and a pilot air inlet port connected to a selectively actuable and deactuable source of pressurized pilot air for selectively actuating and deactuating, respectively, the control system. The control system includes a first control valve device or component that is deactuated when the control system is deactuated for supplying control air from the inlet to the first supply port and for blocking the first supply port from the exhaust port, thus causing the armature to move to the first working position. When such first control valve is actuated, in response to actuation of the control system, it blocks the flow of control air from the inlet to the first supply port and exhausts the first supply port. Similarly, a second control valve is provided and is deactuated when the control system is deactuated for blocking the flow of control air from the inlet to the second supply port and for exhausting the second supply port, with the second control valve being actuated in response to control system actuation for supplying control air from the inlet to the second supply port and for blocking the second supply port from the exhaust, thus causing the armature to move to the second working position.
A control system according to the present invention also includes a timing subsystem that is actuable in order to block flow of the control air from the inlet to the first control valve after the expiration of a predetermined time period following deactuation of the first control valve, thus serving to hold the armature of the pneumatically-operated device in the first working position without the need for continuing to supply control air to the first supply port. Such timing subsystem is deactuated, in response to a control air pressure at the first supply port below a predetermined pressure level, thus allowing control air to be supplied from the inlet to the first control valve. Preferably, the timing subsystem includes a pneumatically-actuated timing valve having a pneumatic actuator, with the timing valve being deactuable for supplying control air from the inlet port to the first control valve and actuable for blocking flow of control air from the inlet to the first control valve. In addition, a flow timer device, which is preferably a timing orifice, is provided and connected in fluid communication between the first supply port and the actuator of the timing valve for supplying control air to the actuator of the timing valve at a predetermined flow rate in order to actuate the timing valve after the above-mentioned predetermined time period.
The preferred control system further includes a check valve in fluid communication with the first supply port for blocking flow through the check valve from the first supply port to the actuator of the timing valve, but freely allowing flow through the check valve from the actuator of the timing valve to the first supply port. Such check valve and the above-mentioned preferred timing orifice are connected in parallel fluid communication between the first supply port and the actuator of the timing valve, and thus work together to cause control air to flow from the first supply port to the actuator of the timing valve only through the timing orifice, while freely allowing flow from the actuator of the timing valve to the system exhaust when the first control valve is actuated in order to exhaust the first supply port.
These features, among other optional features described below that can be incorporated into a control system according to the present invention, serve to enhance the efficient energy usage of the overall system by stabilizing the operation of the control system at a predetermined pressure level necessary to maintain certain static conditions in the pneumatically-operated device, while still providing for full line control air pressure when dynamic portions of the operation are required. In addition, such pneumatic control systems according to the present invention compensate for any leakage occurring in the pneumatically-operated device, or related pneumatic systems, by the use of full line control air pressure only when needed to preserve the proper operating functions of the overall system.
Additional objects, advantages, and features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.